1. Field of the Invention
The present invention generally relates to heat radiating apparatuses for electronic components, and more particularly, to a heat radiating apparatus of an electronic component such as a semiconductor device mounted on a circuit board.
2. Description of the Related Art
An electronic component such as a semiconductor device, like a large scale integration circuit (LSI) or a field programmable gate array (FPGA), is mounted on a circuit board installed in an electronic device such as an information communication device. Such an electronic device is connected to a related device via an optical fiber or the like so that a high speed information transmission and a large amount information transmission are accomplished.
Because of this, the number of components such as the semiconductor device mounted on the circuit board, the optical fiber, a cable, and others is increasing. It is required to mount these components on the circuit board at a high density.
Meanwhile, consumption of electric power in the above-mentioned semiconductor device is increasing as the operating speed of the semiconductor device is being made higher. Hence, a radiator for radiating heat from a surface of the semiconductor device is mounted on the semiconductor device so as to satisfy a junction allowable temperature of the semiconductor device. Since it is required to mount the components on the circuit board at high density as described above, it is desirable that even the radiators be mounted at a space savings.
FIG. 1 is a view showing a conventional radiating apparatus of the semiconductor device. More specifically, FIG. 1-(a) is a plan view of the radiator and FIG. 1-(b) is a side view seen from a direction shown by an arrow A in FIG. 1-(a). See Japan Laid-Open Patent Application No. 6-196883. Referring to FIG. 1, a radiating apparatus 10 includes a radiator 11 and a fixing spring metal fitting 12.
FIG. 2 is a side view of the radiator 11 of the radiating device 10 shown in FIG. 1, seen from a direction shown by an arrow A in FIG. 1-(a). As shown in FIG. 2, the radiator 11 has plural disk-shaped heat radiating fins 11-1 and a cylindrical stud section 11-2. A circumferential groove 11-3 is provided about the circumference of the stud section 11-2 near an end thereof.
As shown in FIG. 1, the fixing spring metal fitting 12 has a spring property and comprises an intermediate piece 12-1 occupying the flat portion and bent pieces 12-2. The bent pieces 12-2 are bent so that the intermediate piece 12-1 overlies the semiconductor device 14 mounted on the circuit board 13 in a generally inverted U shape. The bent pieces 12-2 are inserted into through holes 13-1 so as to be fixed to the circuit board 13.
At the center of the intermediate piece 12-1, a transversely extending, open ended notch 15 is disposed which engages the circumferential groove 11-2 of the radiator 11. The notch 15 comprises an opening portion 15-1 with a width equal to the diameter of the circumferential groove 11-2 of the radiator 11, a semi-circular innermost portion 15-3 with a diameter equal to the diameter of the circumferential groove 11-2 of the radiator 11, and a straight intermediate portion 15-2 connecting the opening portion 15-1 to the innermost portion 15-3. A slot 16 is formed in the intermediate piece 12-1 about the notch 15 so as to surround the notch 15, so that the intermediate piece 12-1 can be deflected vertically (in the up and down direction in FIG. 1-(a)).
Next, the assembly procedure of the heat radiating apparatus 10 is described. The radiator 11 is fixed by the fixing spring metal fitting 12 as follows.
First, the semiconductor device 14 is mounted and fixed to the circuit board 13. The fixing spring metal fitting 12 is mounted to the circuit board 13 so as to overlie the semiconductor device 14. The bent pieces 12-2 are inserted into the through holes 13-1 of the circuit board 13 and bend-fixed or solder-fixed to the circuit board 13 at a position where an inside of the fixing spring metal fitting 12 and a surface of the semiconductor device 14 are mutually opposed.
Then, the circumferential groove 11-3 of the radiator 11 is aligned with the notch 15 of the fixing spring metal fitting 12, and the radiator 11 is slid in a horizontal direction, namely in the left-right direction in FIG. 1-(a), to the central portion of the fixing spring metal fitting 12 from the side. At this time, the end surface of the stud section 11-2 of the radiator 11 goes into a space between the fixing spring metal fitting 12 and the semiconductor device 14. The end surface of the stud section 11-2 of the radiator 11 is in tight contact with and fixed to a top surface of the semiconductor device 14 due to the resiliency of the fixing spring metal fitting 12, thereby heat generated inside of the semiconductor device 14 is radiated by the radiator 11.
However, the above-discussed radiating apparatus 10 has the following problems. More specifically, FIG. 3-(a) is a perspective view of the radiating apparatus 10 and FIG. 3-(b) is a view seen from a direction shown by an arrow B in FIG. 3-(a).
As shown in FIG. 3, in a case where other components such as an optical fiber 17 and circuit elements 18-1 and 18-2 are mounted on the circuit board 13 in a direction in which the radiator 11 is moved, when it is tried to remove the radiator 11 from the fixing spring metal fitting 12 via the opening portion 15-1 of the notch 15 in a direction shown by arrow C, as shown by dotted lines in FIG. 3-(b), the optical fiber 17 and circuit elements 18-1 and 18-2 interfere with the radiator 11. Therefore, it is necessary to move the optical fiber 17 and circuit elements 18-1 and 18-2 in advance before the radiator 11 is removed.
Furthermore, the radiator 11 is installed in the fixing spring metal fitting 12 by putting the radiator 11 in the notch 15 in a horizontal direction, namely from a left to right direction in FIG. 1-(a). Therefore, it is necessary to provide an area within a diameter of the radiating fins 11-1, namely approximately 30 through 40 mm, for installation and removal of the radiator 11. This creates an obstacle to high density mounting of the components on the circuit board.
In addition, in a case where plural electronic components, to which the radiator 11 is required to be mounted, are mounted on the circuit board 13 by placing the electronic components close to each other, in the conventional radiating apparatus 10, there is a limitation in order to provide for the installation and removal of the radiator 11. For example, in a case where wiring of the optical fiber 17 is required so as to wind around and surround the radiator 11 in order to efficiently secure the area where the electronic components are mounted, it is necessary to mount the radiator 11 on the circuit board 13 before the optical fiber 17 is mounted on the circuit board 13.
Furthermore, the radiator 11 itself reaches a high temperature during the operation of the electronic device. Therefore, for example, when a cable such as the optical fiber 17 comes in contact with the radiator 11, the surface of the optical fiber 17 may be damaged. As a result of this, a signal may not be transmitted in the optical fiber 17 normally and thereby bad operations of the electronic device may happen.
Meanwhile, the circumferential groove 11-3 is formed in the radiator 11 so that the radiator 11 is engaged with the fixing spring metal fitting 12. However, the diameter of the stud section 11-2 where the circumferential groove 11-3 is formed in the radiator 11 is small. Hence, thermal conductivity in this part is not good and therefore the radiation effect of the radiator 11 may be an obstacle.
In addition, in the conventional structure, since the force of the fixing spring metal fitting 12 is not applied to the radiator 11 evenly, the thermal conductivity to the radiator 11 is not always good.
Furthermore, in a case where the semiconductor device 14 or the like does not work well, it is required to be able to easily check information indicated on a surface of the semiconductor device 14, such as the manufactures, the type, or the like. However, in the conventional structure, since the area of a notch formed by the notches 15-1 through 15-3 provided for installing the radiator 11 in the fixing spring metal fitting 12 is small, the above-mentioned information indicated on the surface of the semiconductor device 14 may not be always be checked in a state where the radiator 11 is removed. In this case, in order to check the information, it is necessary to remove the fixing spring metal fitting 12.
In addition, it is difficult to lift up the fixing spring metal fitting 12. Hence, it is difficult to easily remove the radiator 11 from the fixing spring metal fitting 12.
Meanwhile, Japan Laid-Open Patent Application No. 4-284654 discloses a radiating structure of a semiconductor device where a radiator is supported by a part made of a shape-memory alloy plate. However, this structure has disadvantages in that the material is limited, the structure is complicated, and the above-mentioned part does not return back to an original state and therefore the radiator cannot be removed before the temperature drops below a designated temperature.